The paper presents major aspects of the assessment of the financial institutions' performance based on the microeconomic theory of companies. The production process of a financial institution in the understanding of Sealey and Lindley (after Frisch) is presented. Their classification of products and inputs allowed the authors to construct a model based on the microeconomic theory of companies. The model was presented in the third chapter of the paper. It is followed by the presentation of an econometric approach to the analysis and assessment of the financial institutions' performance, as an alternative to a traditional approach (based on indicators). The subsequent part of the paper presents categories of microeconomic effectiveness, which is followed by conclusions.